Signal Processing Flashcards

What does the MATLAB `fftshift(X)` function do to the output of `fft`?

Answer: Shifts the zero-frequency component to the center of the spectrum

`fftshift` rearranges the FFT output so that the zero-frequency (DC) component is centered, making two-sided spectra easier to visualize.

Which MATLAB window function call produces a Hamming window of length N?

Answer: hamming(N)

`hamming(N)` returns an N-point Hamming window, a raised cosine with coefficients that minimize the maximum sidelobe level.

What does the MATLAB `hilbert(x)` function return?

Answer: The analytic signal of x, with the original signal as real part and its Hilbert transform as imaginary part

`hilbert(x)` returns the analytic signal, where the real part is x and the imaginary part is the Hilbert transform of x, useful for computing the envelope.

Which MATLAB function designs a Chebyshev Type I IIR lowpass filter with ripple Rp dB in the passband?

Answer: cheby1(n, Rp, Wn)

`cheby1(n, Rp, Wn)` designs a Chebyshev Type I filter that has equiripple in the passband and a monotonic stopband response.

Why is `filtfilt(b, a, x)` preferred over `filter(b, a, x)` in many signal processing applications?

Answer: It achieves zero-phase distortion by filtering the signal forward and backward

`filtfilt` applies the filter twice — once forward and once backward — so phase shifts cancel out, yielding zero phase delay.

In MATLAB's `fft(x, N)`, what does the parameter N specify?

Answer: The number of FFT points (DFT length), zero-padding x if N > length(x)

N sets the DFT length; if N exceeds the signal length, MATLAB zero-pads x to N samples, providing interpolated frequency resolution.

Which MATLAB function directly computes the signal-to-noise ratio (SNR) in dB of a measured signal relative to a reference?

Answer: snr(x, ref)

`snr(x, ref)` computes the SNR in dB by comparing the power of the reference signal to the power of the noise (x minus ref).